This invention relates to a grinder such as for use in grinding materials such as meat, and more particularly to features for use with a grinder which facilitate removal of hard material such as bone, sinew or gristle or other material so that such materials are not ground along with the meat.
In high volume production of ground meat, it is common for the meat being ground to contain hard materials such as bone, sinew, gristle or the like. It is desirable to remove such material prior to or during grinding of the meat, to ensure that the hard material is not ground along with the meat.
A meat grinder typically includes an orifice plate located at the open end of a tubular housing, and a rotating knife assembly provides a series of knives disposed against a surface of the orifice plate. The knives are mounted to a knife holder, which typically comprises a series of radial arms extending outwardly from a central hub. To remove hard material during grinding, it has been known to provide a series of collection orifices toward-the central portion of the orifice plate. With a system of this type, rotation of the knife assembly moves the hard material around the orifice plate, with the hard material eventually making its way toward the center of the orifice plate, where it is received into one of the collection orifices.
A system such as that summarized above generally works satisfactorily to remove hard material from meat during grinding of the meat. However, it has been found that with a lower grade of meat being ground, which contains a greater amount of hard material than higher grade meat, it is nearly impossible for such a system to remove substantially all of the hard material during grinding of the meat.
Accordingly, the present invention has as its object to provide a hard material collection system for use with a meat grinder, which enhances the ability of the grinder to collect hard material during grinding of the meat. It is a further object of the invention to provide a hard material collection system which is used in connection with a conventional grinding system, in which a feed screw advances the meat through a housing toward an orifice plate, and in which a rotating knife assembly is disposed toward the end of the feed screw against the inner surface of the orifice plate. It is further an object of the invention to provide a hard material collection system which is relatively simple in design and in installation, yet which provides a greatly increased ability to collect hard material prior to passing of the hard material through the meat grinding orifices of the orifice plate.
In accordance with one aspect of the invention, a series of spaced collection openings or passages are located toward the center of the orifice plate for collecting hard material such as bone, gristle, sinew or the like. Each collection opening includes a ramped entryway opening onto the surface of the orifice plate facing the knife assembly. The collection openings are relatively large openings, and are located inwardly of relatively small outer openings through which the soft material passes. The ramped entryway to each collection opening extends outwardly toward the outer openings. The collection openings are preferably oval or kidney shaped in plan, and the ramped entryways extend outwardly along one of the long sides of each collection opening. The ramped entryways assist in feeding hard material into the collection openings, and also cooperate with the ends of the collection openings to define shearing edges. When a piece of hard material which is larger than the collection opening is directed into one of the collection openings by the ramped entryway associated therewith, the hard material lodges in the collection opening. Movement of the knife assembly over the collection opening shears off the hard material against the shearing edge defined by the ramped entryway in combination with the end of the collection opening. The portion of the piece of the hard material within the collection opening thereafter passes through the collection opening, and the portion which is sheared off is directed into another collection opening for repeated shearing until it is of a size small enough to pass through a collection opening. The longitudinal axes of the collection passages may either be tangential or radial relative to the center of the orifice plate. When the collection passages are oriented radially, the ramped entryways extend perpendicularly relative to the longitudinal axes of the slots, with the ramped entryways having a width approximately equalling the length of the slots. The ramped entryways are pitched away from the center of the orifice plate, such that the area of greatest depth of each entryway is located at its outermost extent. The edges defined by each ramped entryway and its associated slot function to guide chunks of hard material into the slot while simultaneously shearing the hard material as the knife assembly passes over the entryway and slot.
In accordance with a further aspect of the invention, the hard material is discharged from the collection passages into a hard material collection cavity defined by a collection cup or cone, which further defines a discharge passage for receiving the hard material from the collection cavity. A hard material discharge auger is connected to the outer end of a centering shaft interconnected with the grinder feed screw and rotatable therewith, and the discharge auger extends through the collection cavity into the discharge passage. Rotation of the hard material discharge auger, which is imparted to the hard material discharge auger from the centering shaft, functions to move the collected hard material downstream from the collection cavity to the discharge passage. The hard material is discharged from the discharge passage into a passage defined by a conduit for ultimate discharge into a collection receptacle. The internal walls of the cup or cone defining the collection cavity may be provided with one or more ribs to prevent the collected hard material from simply spinning within the collection cavity, and to ensure that such material continues to move axially downstream toward the discharge passage. Alternatively, flutes may be formed in the discharge passage itself to ensure axial movement of the collected hard material.
In accordance with another aspect of the invention, the rotating knife assembly includes a central hub and a plurality of knife holding arms extending outwardly from the hub, with a knife mounted to each knife holding arm. The arms are arranged so as to be non-radial relative to the hub, thereby providing non-radial mounting of the knives. This arrangement facilitates movement of the hard material inwardly toward the hub during rotation of the knife assembly. In a preferred embodiment, the hub is provided with a collection pocket forwardly of each knife holding arm for receiving hard material moved inwardly toward the hub during rotation of the knife assembly. The collection pockets on the hub are preferably located in alignment with the collection openings in the orifice plate. The collection openings preferably include ramped entryways as described above for facilitating entry of hard material into the collection openings.. Each collection pocket preferably includes an outwardly facing ramped area provided on the hub forwardly of each knife holding arm. In a preferred arrangement, each arm includes a base connected to the hub and an outer end spaced outwardly from the base. Each arm is arranged such that its longitudinal axis is non-parallel to a line extending through its base and through the center of the hub. In this manner, the longitudinal axis of each arm is tangential to a circle concentric with the center of the hub. In a particularly preferred arrangement, the longitudinal axis of each arm is tangential to a common circle concentric with the center of the hub. In one embodiment, the arms are arranged such that the longitudinal axis of each arm is substantially perpendicular to the longitudinal axes of its adjacent arms.
In accordance with yet another aspect of the invention, the knife holder includes a hub and a plurality of knife holding arms extending outwardly therefrom, with a substantially central passage formed in the hub and adapted to receive a centering shaft therethrough. Each knife holding arm has a forwardly opening knife mounting slot formed therein, with each slot opening into the central passage in the hub. A knife mounting pin extends transversely through each knife mounting slot, and is located toward the outer end of each knife holding arm. Each knife is provided with an outwardly opening pin-receiving slot adapted to receive the knife mounting pin therein, wherein the centering shaft and the knife mounting pins cooperate to maintain the knives in position within the slots. This mounting structure acts to positively retain the knives in the knife holder once the centering shaft is inserted through the central passage formed in the hub.
In accordance with a further aspect of the invention, a recovery grinding arrangement is provided downstream of the orifice plate. The recovery grinding arrangement recovers and grinds any soft material which may have passed through the collection openings along with the hard material. The recovery grinding arrangement includes a housing having a rotating recovery knife assembly located within its interior. Material passing through the collection openings is routed to the interior of the housing. In one embodiment, a secondary orifice plate is mounted to the end of the housing, and the soft material is forced by the rotating knife assembly through orifices formed therein. The recovered soft material is then mixed with the ground soft material discharged from the primary orifice plate. In another embodiment, a series of orifices are formed in an upper side wall of the housing. The rotating knife assembly forces the recovered soft material upwardly through the orifices, where it mixes with the soft material discharged from the primary orifice plate. In both embodiments, a discharge tube is connected at the outer end of the housing, and includes an internal passage in communication with the interior of the housing. The hard material is routed by the rotating knife assembly to the internal passage of the discharge tube. A secondary auger is connected to the rotating knife assembly, and is disposed within the internal passage of the discharge tube for passing the hard material therethrough.
In accordance with yet another aspect of the invention, a bushing is mounted within an opening formed in the central portion of the orifice plate for receiving the centering shaft extending from the grinder feed screw. Mating structure, such as a key-and-keyway arrangement, is interposed between the bushing and the orifice plate for maintaining the bushing in a fixed rotational position relative to the orifice plate. The bushing includes a lip which engages the inner surface of the orifice plate, and the opposite end of the bushing includes a set of threads extending past the outer surface of the orifice plate. The bushing extends through a collection cup adaptor which engages the outer surface of the orifice plate, and a threaded ring is engaged with the threads of the bushing. This functions to securely mount the bushing to the orifice plate without the use of threads interposed directly between the bushing and the orifice plate, which have been found to loosen during use, and also provides a highly satisfactory system for mounting the collection cup in position at the downstream surface of the orifice plate. Slots are formed in the collection cup adaptor, and are adapted to align with the hard material collection passages formed in the orifice plate for allowing hard material to pass into the collection cavity. The key-and-keyway arrangement is also interposed between the adaptor and the bushing in order to ensure alignment between the collection passages in the orifice plate and the slots formed in the collection cup adaptor.
In accordance with a still further aspect of the invention, the discharge conduit downstream of the discharge passage may be adapted to receive one of a set of flow controlling nozzle inserts, in order to minimize the discharge of usable soft material into the collection cavity during grinding of the material. Each insert in the set defines a differently sized internal passage, and the inserts are adapted to be removed and replaced according to the conditions of the material being ground and the desired optimum flow rate of the hard material discharge. This controls the back pressure in the collection cavity and in the collection passages, for controlling the quantity of material allowed to pass through the collection passages.
In a particularly preferred embodiment of the invention, the various aspects and features as summarized above may be combined into a single structure for facilitating advancing of hard material toward the center of the orifice plate during grinding and passage of the hard material into the collection openings or passages formed in the orifice plate, and for recovering soft material which may pass through the collection openings along with the hard material.
Various other features, advantages and objects of the invention will be made apparent from the following description taken together with the drawings.